Spanish Colonial architecture in the New World is a synthesis of several influences that span many centuries.
These include the Roman Empire (via original structures, and the re-discovery of the works of Roman architect Marcus Vitruvius Pollio in 1511 A.D.), the Islamic Moors of North Africa, and Christian Europe.
Classical, Moorish, and Gothic influences melded in the 1500s, to produce the Spanish art style known as plateresque. In the New World, the term was soon applied to architecture as well.
See the rest of the story in this week's Advance-Guard.